Blood Sugar Monitoring
The American Diabetes Association published revised Standards of Care for
diabetes, emphasizing that high-quality diabetes care must be individualized to
reflect the needs, interests, and abilities of each person. The primary goal of
care is to reduce blood glucose levels to as close to normal as is reasonable.
To monitor success toward that goal, the diabetic should self-manage in a
responsible manner using diet revision and exercise as the primary strategy and
should self-monitor blood glucose levels at home.
The secondary goal is to
monitor for and, if detected, treat developing complications. This
requires annual eye exams to detect retinopathy, annual urinalysis to search for
early signs of nephropathy, periodic foot examinations, regular blood pressure
and cholesterol and triglyceride testing to warn of impending heart disease. The
official view is that patient education and motivation must be a central
component of quality diabetes care because each person must provide daily
- managing food selection, meal planning
- staying in control of the diet
- getting daily exercise
- self-monitoring blood glucose
- taking medication, if required
- quitting smoking
Blood Sugar Monitoring
Home testing of blood glucose levels is useful for the self-managing
diabetic. You have to remember that the reason for doing a test is to provide
you with information that influences the decisions you make. An insulin
dependent diabetic will make decisions about the dose and timing of
insulin injections based on blood glucose levels. Blood glucose
measurements are required to make good decisions about adjusting the insulin
dose. A person with early type 2 diabetes will need less frequent blood glucose
measurements to guide food choices and adjust activity levels.
Several testing units are available and all are relatively easy to use. There
are two blood sugar scales in use - the metric system mmol/l and the older mg/dl
scale. The most important number is 7 mmol/l = 120 mg/dl - the upper limits of
normal range for fasting blood sugar and 2 hours after-eating blood sugar.
Margin of Error and Different Blood Glucose Scales
Blood glucose values in medical publications are measured from venous blood
drawn from your arm. Test results vary depending on the age of the blood sample
and the calibration of lab instruments. There are no measurements without error.
A properly calibrated machine will have a known error range. Glucometers are
reasonable devices for home monitoring that will track changes in blood glucose
although up to 10% error can be assumed so that decisions based on small decimal
point differences are not appropriate.
At home, you prick your skin and test blood from capillaries under the skin
where glucose content tends to be higher than venous blood. Capillary glucose
values may be 0.5 to 3 mmol/L higher than venous blood values. Also, capillary
values vary with the skin puncture location. Finger tips are often used, but
have more nerve ends and a smaller surface area. Samples taken from the palms of
the hands are also reliable. Finger tip and palm blood samples respond quickly
to changes in blood glucose. Forearm samples are slower to change. When blood
glucose is rising quickly after a meal, finger tip readings can be up to 3 mmol
higher than venous blood samples. All tests results are approximations that
include some variation. In other words, a capillary reading of 7.4 in the
morning may be considered "normal" in terms of a venous blood standard of normal
(less than 7.)
Ames stated in its glucometer instructions that venous blood levels are 7%
lower than capillary readings. One touch meters are calibrated so that finger
sample tests better correspond with readings from venous blood done in a lab.
Usually, meter calibration information is in the fine print of the product
description that comes with the device.
Some test strips are small and anyone with hand or visual difficulties will
have difficulty placing the strip into the measuring device and touching the
strip in the right place to a small drop of blood. Some meters can
download data and have associated software that tracks blood glucose values over
time. The OneTouch Ultrasmart device retains data, permits the entry of
additional data such as exercise, insulin and medication and presents a variety
of useful reports. Some training is required to make good use of this device.
Three glucose measurements are useful for different reasons
Fasting blood glucose levels, taken in the morning before eating,
should fall in a normal range. The goal is to keep this value under 7 mmol/L or
120 mg/dl. (glucometer test values up to 8.0mmol)
Two hours after eating: blood sugar rises and then falls to a baseline
level. By sampling blood sugar levels two hours after eating, you find out if
glucose is being removed from your blood in a reasonable time. The sugar level
peaks in 30-60 minutes and the falls back to a baseline level. The timing and
height of the peak level will vary with the composition of the meal and activity
levels. The glycemic index has been developed to show the peak sugar response
after eating individual foods.
The goal is to show values less than 7 mmol or 120 mg at two hours. Higher
values tell you that you must do two things- change the food or meal that caused
high sugar level and exercise after the meal to increase glucose utilization.
Checking symptomatic episodes: you measure blood sugar when you are
not feeling well to find out how your symptoms correlate with the blood sugar
level. High levels are associated with an intoxicated feeling - drowsy, hard to
concentrate, judgment impaired. Levels above 17 mmol or 300 mg are dangerously
high - you are likely to want to sleep at this level but the most effective way
to reduce the sugar levels is to exercise as vigorously as you can.
Levels below 4.5 capillary may be associated with hypoglycemic symptoms - you
feel strange, anxious, irritable; a tremor develops if the blood sugar
value falls lower and you become desperate to eat something. If you can take a
quick sugar hit - a glass of orange juice will do and measure your sugar
immediately you can determine how low the value dropped; as you feel better do
another blood sugar check to find the value that feels normal.
Hemoglobin A1C (HbA1c)
High levels of blood glucose lead to glycosylation reactions with a variety
of proteins. Glycated protein macromolecules become malformed, cross-linked
polymers and are believed to play a significant role in the development of the
complications of diabetes. Therapy is aimed at minimizing the formation of these
cross-linked proteins by lowering the average blood glucose concentrations.
Diabetic patients are encouraged to undergo routine monitoring of the levels
of the cross-linked molecule, hemoglobin A1C (HbA1c), as a marker of long-term
glycemic control. Glycated hemoglobin is assayed in a sample of blood. Red blood
cells have a life span of 90 to 120 days, HbA1c readings provide a good
indication of the average glucose control over the past 90 days but will not
show a recent change. The goal is to keep HBA1c at less than 7 percent (of the
While self monitoring works best if good records are kept and reviewed
regularly, I discovered that only a small number of technical enthusiasts with
DB2 will use all the features of glucose monitoring devices and keep adequate
records long term. I also discovered that very few people will use nutrient
analysis and meal planning software, even when good programs are available
online at low cost. Professionals monitoring patients also will seldom use daily
monitoring and meal planning software because it is too time consuming.